N-acetyl-L-cysteine is a well known compound which is routinely used as a therapeutic agent against chronic obstructive pulmonary diseases, particularly chronic bronchitis. The mode of action of the compound is not fully clarified but it is considered that the compound acts as a mycolytic agent or an antioxidant. Reduction of the degree of exacerbations in patients suffering from chronic bronchitis has been reported for N-acetyl-L-cysteine. A possible explanation for this effect could be that the compound enhances the host defence in these patents (see Bergstrand, H. et al J. Free Radic. Biol. Med. 2, 119-127, 1986).
The corresponding disulphide of N-acetyl-L-cysteine, N,N'-diacetylcystine (DiNAC), is a potent immunostimulator as revealed by its capacity to enhance a contact sensitivity reaction in mice.